1. Field of the Invention
This invention relates to abrasive materials and, more particularly, to methods for making sintered aluminous abrasive materials which may be utilized in products such as grinding wheels and in other abrasive applications.
2. Description of the Prior Art
The production of aluminous abrasive materials is well known. The two most common production techniques are the arc furnace technique and the sintering technique. In the arc furnace technique, the final product is generally known as a fused abrasive. In the sintering technique, the final product is generally known as a sintered abrasive. Both the fused abrasive materials and the sintered abrasive materials may be utilized in similar types of products.
In the arc furnace technique, the final abrasive material product is called fused because it results from a melting operation. Typically, such operations are costly, particularly because of the energy-intensive nature of the process. Such operations may also be dangerous due to the extremely high temperatures of fabrication involved. The temperatures involved are normally about 2000.degree. C. At such temperatures, arc furnaces are prone to erupting and spewing forth quantities of molten alumina as a result of gas formation within the furnaces. In addition, the individual abrasive grains obtained via this process are produced by crushing large pieces of solidified furnace product. This is followed by collecting and screening out the various resultant sizes. Naturally, a whole range of sizes is produced, some of which are more in demand by the market than are others. A certain degree of control may be exercised during the crushing operations in order to minimize the production of particles of unwanted sizes. Their occurrence, however, persists and remains troublesome and expensive to manufactures of aluminous abrasives.
Sintered abrasives have been manufactured in the past in an attempt to reduce not only the operating temperatures required, but also the attendant potential hazards and the expense of making the abrasive grain particles of unwanted sizes. These sintered abrasives have been generally made from previously processed bauxite, specifically calcined bauxite and normally include a process which includes the step of milling. Such milling step, most often ball milling, can extend up to 24 hours in duration and normally results in a fine powder, typically a 5 micron average particle size. This powder is normally formed into granules and then sintered to form abrasive grains with essentially no unwanted sizes.
The present invention has for its objectives the manufacture of commercially acceptable sintered aluminous abrasive materials by improved methods which overcome many of the above mentioned disadvantages and shortcomings of the prior art. The method of the present invention eliminates the need for employing the arc furnace of the fusing method along with its attendant high temperatures, potential for dangerous explosions and excessively high costs. Also, the resulting powder is of a considerably greater surface area than that produced by the prior art sintering method by virtue of a finer particle size. This finer particle size results in a more highly reactive and more sinterable powder. In addition, the present method is advantageous as compared with the prior art sintering process since the slow milling step is avoided. The present invention also utilizes the less desirable production by-products of the manufacturing process in further processing for greater efficiency and economy of operation, as opposed to the fusing method.
The foregoing has outlined some of the more pertinent objects and advantages of the present invention. These objects and advantages should be construed to be merely illustrative of some of the more prominent features and applications of the instant invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and advantages and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description describing the preferred and alternate embodiments and examples in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawing.